The archetypes are approached by Jung in his entire work. But in his book on the confrontation between the ego and the unconscious, he describes the process of psychical
assimilation of the unconscious, which is made of archetypes or more specifically of archetypal images. Among all these, he mentions: Shadow, Anima/Animus andthe Wise Old Man.

But what is the archetype? An innate tendency which molds and transform the individual consciousness. A fact defined more through a drive
than through specific inherited contents, images etc.; a matrix which influences the human behavior as well as his ideas and concepts on the ethical, moral religious and cultural levels.

Jung talks about
the archetype (also called "primordial image") as of biologists' patterns of behavior (inborn behavior patterns). In short, archetypes are inborn tendencies which shape the human behavior.

"The archetype concept - Jung writes - derives from the often repeated observation that myths and universal literature stories contain well defined themes which appear every time and everywhere. We often meet these
themes in the fantasies, dreams, delirious ideas and illusions of persons living nowadays".

These themes are representations of archetypes; they are based on archetypes. They impress, influence and
fascinate us (our ego). This is why we call their tremendous effect numinous - that is, able to arise deep and intense emotions.

Archetypes do not have a well defined shape "but from the moment they become
conscious, namely nurtured with the stuff of conscious experience." Basically an archetype is empty, purely formal, nothing else but a pre-shaping possibility or an innate tendency of shaping things.

We can
say that archetypes resemble the instincts in that that they cannot be recognized as such until they manifest in intention or action.

Finally, the archetype is psychoid (psychic-like); it shares both
psychic and material aspects and acts as well on a psychic and/or material plane. (See also the synchronicity principle).